Tube forming device



Oct. il, 1949. F. v. coLLlNs TUBE FORMING DEVICE Filed March 24, 1947 E@ E E Patented Oct. 11, 1949 OFFICE TUBE FoaMlNc DEVICE Fred V. Collins, Des Plaines, lll., assignor to William F. Stahl, Kenilworth, Ill.

Application March 24, 1947, Serial No. 736,760

6 Claims. (Cl. 154-42) This invention relates to a tube-forming device and is particularly useful in the forming of tubes from flat fusible stock.

An object of the present invention is to provide improved means for the forming of tubes from fiat stock and more particularly through the fusing of the edge portions of the plastic material. Another object is to provide means for continuously forming a tube about a mandrel while permitting the tube to be drawn off and rolled upon itself in a plane transverse of its longitudinal axis. Yet another object is to provide a mechanism particularly effective in the fusing of edge portions of flat material when rolled into tubular form and for subjecting the edge portions to the action of'high frequency radio waves. Other specific objects and advantages will appear as the specification proceeds.

The invention is illustrated, in a preferred embodiment, by the accompanying drawing, in Which- Figure 1 is a broken longitudinal sectional view of apparatus embodying my invention; and Fig. 2, a transverse sectional view, the section being taken as indicated at line 2 of Fig. l.

In the illustration given, I designates a mandrel toward which a dat plastic sheet II is fed to form a tube I2. The completed tube is drawn forwardly and discharged from the front free end of the mandrel I0 by rollers I3 provided with resilient tires I4. Such structure is described in greater detail in my copending application, Serial No. 651,642, for Tube-forming apparatus and method. As described more fully in said application, the flat web I I is folded about the mandrel III so as to engage it. The free ends of the web II pass through slots in the folding member I5 and thence on through a tubular guide or folder I6 where the folding is completed. The overlapping edge portions of the tube pass under the electronic foot I1 where they are subjected to high frequency radio waves to bring about the fusion of such edge portions and the completion of the tube.

The mandrel I0 is formed of several parts. The rear portion I8 is illustrated as formed of metal having a longitudinal passage I9. It is threadedly connected to a similar section 20 having also a longitudinal passage. Another section 2| extends between the rollers I3. The sections 20 and 2| are separated and spaced apart by an insulating segment 22 formed of Bakelite or any other suitable electrical insulation material. The segment 22 and the section 2I arev also-provided with central passages so that the entire mandrel 2 III has a continuous longitudinal passage extending therethrough.

I prefer to reduce the segment 22 of insulating material in diameter so that the plastic tube I2 will not touch it as it is advanced upon the mandrel.

Any suitable means for supporting the mandrel may be employed. In the illustration given, I providea beam 23 carried by the frame of the machine and secured by bolts 24 to the mandrel. Upon the stepped portion 25 of member 23, I secure an arm 26 by means of a bolt 21. The arm is provided with spring jaws at its forward end adapted to receive the shank 28 of the electronic foot II and to releasably clamp it in position by means of bolts 29. Current is supplied to the member I8 by the concentric line 30, and the shield 3| is grounded through the cable 32.

The folding member I6 is supported by means of an arm 33 having a standard 34 secured to the mandrel I0.

I have found that certain distances are critical in effective operation of the device. For example, the distance between the insulating segment 22 and the point of the mandrel aligned with the rear of the supporting member 23 should be substantially equal to a multiple of a quarter of one wave length. The same is true of the distance between the forward end of shield 3I and the center of the riser 35 which supports the shield 3|. The same rule applies to the portion of the concentric line between the forward edge of the shield 3I and the electronic foot I1; that is, this distance represented by the lengths of this forward section 30 of the concentric line and by the portions 28 and I1 of the electronic foot should be substantially equal to a multiple of a onequarter wave length. The first distance referred to above extends between the letters A and B, as shown in Fig. l, The second distance referred to is indicated by the letters C and D. 'I'he third distance is indicated by the length of the parts between the letter C and the bottom of the electronic foot I1. This produces a matching of impedances of the output of the generator and the termination load end of the line.

Operation In the operation of the device, a flat sheet II is fed forwardly with the free edges of the sheet being drawn upwardly to envelope the mandrel I0. Such free edges pass through slots in the guide member I5 and thence on downwardly through the folding device I6 where the upper edges of the sheet are brought into overlapping relation and pass under the electronic foot I1. Here the dielectric tube material is subjected to the action of high frequency radio waves which bring about a fusion of such overlapping parts. The members I3 are rotated so as to draw the tube I2 forwardly and project it over the free end of the mandrel. Here, if desired, the tube may be folded upon itself in a direction transverse of its longitudinal axis, the folding or rolling being done manually or by mechanical parts. In this operation, air from within the tube escapes through the longitudinal passage I9 of the mandrel I0.

The insulating segment 22 prevents the mandrel from becoming a J or like antenna radiating system which would change the phase relationship between the voltage and current on the mandrel.

To obtain the maximum power at the electronic foot, the Voltage and current should be in the proper phase relationship to produce the correct matching of impedances of the generator output and the line termination. By maintaining the distances between the letters A and B as substantially equal to a multiple of one-quarter of a Wave length, the best results are produced. The same applies to the distance indicated between the letters C and D and between the letter C and the bottom of the electronic foot II.

The tube material II may be of any suitable material. Excellent results have been obtained in treating plastic materials such as cellulose acetate, vinyl acetate, vinyl chloride (co-polymer), etc. In the treatment of such material, a relatively high range of frequency may be employed depending upon the thickness of the material being utilized, its power factor, dielectric strength, etc. Frequencies of 200 megacycles have been found successful with such materials. The effect of the high frequency radio waves is to bring about an internal change in the web so that a fusion occurs between the overlapping or adjacent walls, thus forming an integral seam. The electronic foot Il is connected through the cable 30 to a radio frequency generator (not shown) and in the resulting fusion operation, the electronic foot I1 serves as one electrode and the mandrel I as the other.

Instead of having the tube walls overlap just below the electronic foot Il, the edges of the tube may be brought together in parallel relation and fused by the action of the high frequency radio waves while in this relationship.

While in the foregoing specification, I have described the apparatus in great detail for the purpose of showing one embodiment of the invention, it will be understood that such details may be varied widely by those skilled in the art without departing from the spirit of my invention.

I claim:

l. Apparatus for forming tubes from fusible fiat web material, comprising a mandrel formed of electric-conducting material, means for supporting the mandrel, means for forming said web in tubular form about said mandrel, means for subjecting the edge portions of said tube to the action of high frequency radio waves to fuse said edge portions, and an electric insulation segment interposed in said mandrel forwardly of said last-mentioned means at a distance therefrom substantially equal to an integral multiple of a quarter-wavelength of said radio waves.

2. Apparatus for forming tubes from fusible flat web material, comprising a mandrel, means for supporting the mandrel, means for drawing said web forwardly of said mandrel and into tubular form, means for subjecting the edge portions of said tube to the action of high frequency radio waves to fuse said portions, and an electric insulation segment interposed in said mandrel between said last-mentioned means and said tube drawing means at a distance from said lastmentioned means substantially equal to an integral multiple of a quarter-wavelength of said radio waves.

3. Apparatus for forming tubes from fiat web material fusible under the influence of high frequency radio waves, comprising a mandrel formed of metal but having an insulation segment therein separating the metal parts, means for drawing said web material about said mandrel into general tubular form with the side portions of the web in contiguous relation, and means for subjecting said contiguous portions of the web to the action of high frequency radio waves to fuse them together, said mandrel having an air relief passage extending longitudinally therethrough and said last-mentioned means being positioned at a distance from said insulating segment substantially equal to an integral multiple of a quarter-wavelength of said radio waves.

4. Apparatus for forming tubes from fusible flat web material, comprising a mandrel, a support for said mandrel, means for forming a web into tubular form about said mandrel, means supported by said mandrel for subjecting the overlapping edges of said web to the action of high frequency radio waves to fuse them together, and an insulation block interposed in said mandrel at a point forward of said last-mentioned means, the distance Ybetween the rear portion of said mandrel support and the rear end portion of said insulation block constituting substantially a multiple of a quarter of a wave length of said radio waves.

5. Apparatus for forming tubes from fusible flat web material, comprising a mandrel, means for supporting said mandrel, means for forming a web into tubular form which overlaps and positions about said mandrel, an electronic foot supported above said mandrel and over said overlapping portions of the tube, a concentric line joined to said electronic foot adapted to supply radio-frequency current thereto and equipped with a grounded shield, the forward end of said shield and the rear point of support for said shield being separated by a distance substantially equal to a multiple of a quarter of a wave length of said radio-frequency current.

6. Apparatus for forming tubes from flat web material fusible under the influence of high frequency radio waves, comprising a mandrel, supporting means therefor, means for drawing said web material into tubular form about said mandrel with the edges of thematerial brought together, an electronic foot supported above said mandrel and over said overlapping edges, a concentric line connected to said electronic foot adapted to carry radio-frequency current thereto and having a grounded shield terminating short of said foot, the length of said electronic foot and the concentric line leading to said shield being substantially equal to a multiple of a onequarter wave length of said radio-frequency current.

FRED V. COLLINS.

(References on following page) REFERENCES CITED FOREIGN PATENTS The following references are of record in the Number Country A Date le of this patent: 555,054 Great Britain Aug. 3, 1943 UNITED STATES PATENTS 5 OTHER REFERENCES Number Name Date Reprint from the August 1943 issue of Elec- 2,114,625 Bergstein 1 Apr. 19, 1938 tronies, An.E1ectronic Sewing Machine, by 2,145,941 Maxeld Feb. 7, 1939 Cyril N. Hoyler, R. C. A. Laib.,` Princeton, New

2,434,330 Merz et al Jan. 13, 1948 10 Jersey. 

